1. FIELD OF THE INVENTION
The present invention relates to an image retrieval method and apparatus suitable for retrieving document image files.
2. DESCRIPTION OF THE PRIOR ART
Of conventional retrieval methods for image files, the two most fundamental methods may be noted, of which one is to directly specify data names to be retrieved and the other to select a desired image from candidate data displayed in accordance with a specified classification code (indicative of, for example, major or middle classification). Known as advanced retrieval methods are, for example, a map image data base related to topographic figures in a map (reference (1) below), a query by pictorial example (QPE) in which an image file is retrieved by using a pictorial example (reference (2)), a method utilizing graphical expression of information related to data to be retrieved (references (1) and (2)), a method in which correspondence is made to color suggested by association from data contents (reference (3)), and retrieval of a series of Chinese character patterns using feature parameters (reference (4)).
References (Japanese language)
(1) "Image Data Base under Advanced Research Directed to Practical Utilization", Nikkei Computer, May 31, 1982, pp 40-49.
(2) Japanese Patent Application Laid-open No. 57-109050 laid open July 7, 1982.
(3) Japanese Patent Application Laid-open No. 57-121767 laid open July 29, 1982.
(4) "Retrieval of a Series of Chinese Character Patterns Using Feature Parameters", by Ohta et al, the Institute of Electronics and Communication Engineers of Japan, Research section, paper No. IE 80-120, pp 91-98.
Incidentally, as apparent from experiences in everyday life, memo information added by a user to data in a file will give a significant clue or guidance to retrieving the file in the future. By experience, it is also easy to decide what data an original image is related to by referring to a specified sub-image (for example, a portrait on a customer card or a structural diagram of a specified portion of a device) of the original image. In some applications (for example, retrieval of a cutout of newspaper, an interleaf for a book, or a note designated by an underline or marked in red), contents are referred to by positively making the most of only a sub-image rather than the entire image. In the past, however, methods have not yet been available which make the most of memo information such as reference information and a sub-image in order to retrieve an image file, leading to inevitable impairment of operational efficiency.